Tong-type clamps have been in widespread use for various purposes, e.g., as ice tongs, wood clamps, and as various types of carriers. These types of clamps include a pair of clamping members which are pivotally connected to one another intermediate their ends. The portions of the clamping members extending in one direction from the pivot connection serve as handles for the clamp and the portions of the members extending in the other direction from the pivot connection serve as the clamping arms.
The clamping arms terminate in facing clamping jaws which are adapted to grip a workpiece therebetween. As the handles are moved toward one another the clamping arms correspondingly move together. Thus, in a lifting operation the heavier the workpiece, the more force exerted in moving the handle members toward one another and the tighter the grip exerted on the workpiece by the clamp jaws as the workpiece is lifted by the clamp.
These tong-type clamps have previously been provided with a locking mechanism to maintain the clamp in a set locked position. This is to minimize the danger of the workpiece being released from the clamp as it is being handled.
Various types of locking mechanisms have been previously used, as described in U.S. Pat. Nos. 2,301,079; 2,705,659; 2,059,972; 3,241,352; and 3,696,653. A preferred type of locking member is described in my prior patent, U.S. Pat. No. 3,870,359. This type of locking mechanism involves a movable cam member which is mounted on one of the clamping arms of the tong-type clamp.
A problem which is common to all of the tong-type clamps, however, is that the clamp must be pulled straight in order to maintain a tight grip upon the workpiece. Thus, such tong-type clamps cannot be pulled to the side or at an angle or else the clamp may lose its grip upon the workpiece. Thus, if a large pulling force is to be exerted upon the tong-type clamp then the pulling force must be generally in line with the central longitudinal axis of the clamp in order to assure that the clamp will not become separated from the workpiece.
In some situations, however, it may not be possible or it may not be desired to only exert a straight pulling force on a tong-type clamp. For example, in the automobile repair business it is often necessary to straighten an automobile body or frame by pulling the frame or body at a certain angle. It may not be possible or practical to align the tong-type clamp in the same direction as the pulling force which is required to straighten the body or frame. In such situations, if a conventional tong-type clamp is fastened to the workpiece and then pulled at an angle to the clamp, or is pulled sideways, for example, the clamp will probably be pulled loose from the workpiece because it is not capable of maintaining its gripping force when being pulled at such an angle. Even the presence of a locking means to maintain the clamping jaws in closed position may not be sufficient to overcome the tremendous force involved in pulling on the clamp at an angle when straightening an automobile body or frame or in other heavy duty operations.
There has not heretofore been provided a tong-type clamp which is suitable for pulling at any desired angle in heavy-duty situations.